HARDWAREMONTAGES ★ The proof is in the printing: expand your Amstrad DMP 2000 s buffer to 8K ★

Expand Your Amstrad Dmp 2000 Buffer To 8k|Popular Computing Weekly)Hardware Montages
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Dave Race explains how to expand your Amstrad DMP 2000's buffer to 8K

Amongst other great features the Amstrad DMP 2000 printer comes complete with a 2K buffer, which siores characters sent from the computer and allows the computer to carry on computing instead of having to wait for the printer to finish printing.
Unfortunately it is not really a 2K buffer, despite there being a 2K Ram chip inside the printer. This is because the printer uses some of this memory itself and some is used for the line buffer, which stores the line about to be printed.

In fact the actual printer buffer is only half a kilobyte which obviously won't store very much text at all. slightly less than this paragraph in fact. This means that in reality your computer will still have to wait for the printer to catch up with it.

Figure two - printer PCB

However, I have discovered that it is possible to expand the printer buffer some seven fold, thus allowing reasonably large chunks of text to be sent to the printer without holding up the computer.

It should be noted that fitting this extra memory will almost certainly invalidate the Amstrad warranty and so should only be carried out on machines over a year old, or by owners who don't mind paying for any repairs if their printer goes wrong. That warning out of the way, on with the instructions.
The extra memory comes form fitting an 8K RAM chip in the printer in place of the 2K chip already there. The chip you will need is a 6164, available from RS (ref 301-870) for about a fiver. Also you will need a small Posidrive screwdriver, a small flat bladed screwdriver, a sharp blade (a scalpel is perfect), and a soldering iron with a fairly small tip.

To begin with ensure that the mains lead is unplugged. It is not sufficient to simply switch the printer off, and you must check there is no paper or ribbon in the printer.

Now turn the printer over so you have access to the bottom (you'll probably want to put the lid to one side). You will be able to see six Posidrive screws, three at the front and three at the back, unscrew and remove these - and put them somewhere safe Turn the printer back over and remove the top half; this is best done with the friction/tractor switch in the friction position. Lift the top half up, tilt it forward, and you will see that there is a ribbon cable going from the push button panel to a printed circuit board in the bottom half. Unplug this at the PCB end and you will be able to remove the top completely.

Figure one — J3 viewed from solder side of board

If you examine this PCB you will see six more leads going 10 it. Remove all these carefully, making note of where each goes. You also need to unscrew the two Posidrive screws that seem to be holding the Centronics connector in place. The PCB can now be removed by lifting it up from the rear and pulling it out backwards. Place the PCB on your work-surface, preferably on a piece of cardboard to give it some protection. It should not be placed on a metal surface.

Remove the 2K Ram chip (see figure two). This is best done by levering the chip up at both ends in turn with the flat bladed screwdriver until it comes free. The 8K chip goes in the socket you have just emptied. If you look closely at the chip you will see it has a small indentation at one end, which must be orientated the same way as in the diagram, ie, with the indentation towards the rear of the board. When inserting the chip it is very important to check that no legs are bent. It is also a good idea to touch something that is earthed before hand ling the chip as it is quite sensitive to static electricity.
Now comes the bit that the warranty won't like. Locate the three pads marked J3 on the top of the PCB, turn the board over and find them on the back, they aren't marked on the solder side. You will see that one of the pads is tracked to the centre one (see figure one), and you must cut this track. Be very careful not to cut any other tracks, but on the other hand ensure that the two pads are no longer joined Next join the other outer pad to centre one, this is best done by soldering a piece of mod wire between them but could be done with just a blob of solder if you are careful. Obviously you should not join any other tracks together in the process. It is advisable to check your handiwork very carefully, with a magnifying glass if necessary.

The printer can be put back together now in the reverse order to' the instructions above, being careful not to damage any of the cables going to the PCB. Once back together power the printer up and try sending a listing to it. You should be able to see quite an improvement.


The table below shows just how great an increase in memory is provided
ModeInternal
Ram
Receiving
buffer
Line
buffer
Download
characters
Dipswitch
2-3    2-4
Character2
8
0.5
6.5
0.9
0.9
0
0
off off
Graphic2
8
0.4
5.7
1.2
1.8
0
0
on off
Download2
8
0.2
3.6
0.9
0.9
32
256
off on
Download
Graphic
2
8
0.2
2.7
0.9
1.8
32
256
on on

 

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★ ANNÉE: ???
★ AUTHOR: Dave Race

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» Hardware » Imprimante - Amstrad DMP 2000
» Hardware » Imprimante - Amstrad DMP 3000

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L'Amstrad CPC est une machine 8 bits à base d'un Z80 à 4MHz. Le premier de la gamme fut le CPC 464 en 1984, équipé d'un lecteur de cassettes intégré il se plaçait en concurrent  du Commodore C64 beaucoup plus compliqué à utiliser et plus cher. Ce fut un réel succès et sorti cette même années le CPC 664 équipé d'un lecteur de disquettes trois pouces intégré. Sa vie fut de courte durée puisqu'en 1985 il fut remplacé par le CPC 6128 qui était plus compact, plus soigné et surtout qui avait 128Ko de RAM au lieu de 64Ko.